/*
 * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
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 *
 *
 *
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 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.naming.internal;

import java.io.InputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URLClassLoader;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.Properties;

import javax.naming.*;

/**
 * VersionHelper was used by JNDI to accommodate differences between
 * JDK 1.1.x and the Java 2 platform. As this is no longer necessary
 * since JNDI's inclusion in the platform, this class currently
 * serves as a set of utilities for performing system-level things,
 * such as class-loading and reading system properties.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 */

final class VersionHelper12 extends VersionHelper {

  // Disallow external from creating one of these.
  VersionHelper12() {
  }

  public Class<?> loadClass(String className) throws ClassNotFoundException {
    return loadClass(className, getContextClassLoader());
  }

  /**
   * Package private.
   *
   * This internal method is used with Thread Context Class Loader (TCCL),
   * please don't expose this method as public.
   */
  Class<?> loadClass(String className, ClassLoader cl)
      throws ClassNotFoundException {
    Class<?> cls = Class.forName(className, true, cl);
    return cls;
  }

  /**
   * @param className A non-null fully qualified class name.
   * @param codebase A non-null, space-separated list of URL strings.
   */
  public Class<?> loadClass(String className, String codebase)
      throws ClassNotFoundException, MalformedURLException {

    ClassLoader parent = getContextClassLoader();
    ClassLoader cl =
        URLClassLoader.newInstance(getUrlArray(codebase), parent);

    return loadClass(className, cl);
  }

  String getJndiProperty(final int i) {
    return AccessController.doPrivileged(
        new PrivilegedAction<String>() {
          public String run() {
            try {
              return System.getProperty(PROPS[i]);
            } catch (SecurityException e) {
              return null;
            }
          }
        }
    );
  }

  String[] getJndiProperties() {
    Properties sysProps = AccessController.doPrivileged(
        new PrivilegedAction<Properties>() {
          public Properties run() {
            try {
              return System.getProperties();
            } catch (SecurityException e) {
              return null;
            }
          }
        }
    );
    if (sysProps == null) {
      return null;
    }
    String[] jProps = new String[PROPS.length];
    for (int i = 0; i < PROPS.length; i++) {
      jProps[i] = sysProps.getProperty(PROPS[i]);
    }
    return jProps;
  }

  InputStream getResourceAsStream(final Class<?> c, final String name) {
    return AccessController.doPrivileged(
        new PrivilegedAction<InputStream>() {
          public InputStream run() {
            return c.getResourceAsStream(name);
          }
        }
    );
  }

  InputStream getJavaHomeLibStream(final String filename) {
    return AccessController.doPrivileged(
        new PrivilegedAction<InputStream>() {
          public InputStream run() {
            try {
              String javahome = System.getProperty("java.home");
              if (javahome == null) {
                return null;
              }
              String pathname = javahome + java.io.File.separator +
                  "lib" + java.io.File.separator + filename;
              return new java.io.FileInputStream(pathname);
            } catch (Exception e) {
              return null;
            }
          }
        }
    );
  }

  NamingEnumeration<InputStream> getResources(final ClassLoader cl,
      final String name) throws IOException {
    Enumeration<URL> urls;
    try {
      urls = AccessController.doPrivileged(
          new PrivilegedExceptionAction<Enumeration<URL>>() {
            public Enumeration<URL> run() throws IOException {
              return (cl == null)
                  ? ClassLoader.getSystemResources(name)
                  : cl.getResources(name);
            }
          }
      );
    } catch (PrivilegedActionException e) {
      throw (IOException) e.getException();
    }
    return new InputStreamEnumeration(urls);
  }

  /**
   * Package private.
   *
   * This internal method returns Thread Context Class Loader (TCCL),
   * if null, returns the system Class Loader.
   *
   * Please don't expose this method as public.
   */
  ClassLoader getContextClassLoader() {

    return AccessController.doPrivileged(
        new PrivilegedAction<ClassLoader>() {
          public ClassLoader run() {
            ClassLoader loader =
                Thread.currentThread().getContextClassLoader();
            if (loader == null) {
              // Don't use bootstrap class loader directly!
              loader = ClassLoader.getSystemClassLoader();
            }

            return loader;
          }
        }
    );
  }

  /**
   * Given an enumeration of URLs, an instance of this class represents
   * an enumeration of their InputStreams.  Each operation on the URL
   * enumeration is performed within a doPrivileged block.
   * This is used to enumerate the resources under a foreign codebase.
   * This class is not MT-safe.
   */
  class InputStreamEnumeration implements NamingEnumeration<InputStream> {

    private final Enumeration<URL> urls;

    private InputStream nextElement = null;

    InputStreamEnumeration(Enumeration<URL> urls) {
      this.urls = urls;
    }

    /*
     * Returns the next InputStream, or null if there are no more.
     * An InputStream that cannot be opened is skipped.
     */
    private InputStream getNextElement() {
      return AccessController.doPrivileged(
          new PrivilegedAction<InputStream>() {
            public InputStream run() {
              while (urls.hasMoreElements()) {
                try {
                  return urls.nextElement().openStream();
                } catch (IOException e) {
                  // skip this URL
                }
              }
              return null;
            }
          }
      );
    }

    public boolean hasMore() {
      if (nextElement != null) {
        return true;
      }
      nextElement = getNextElement();
      return (nextElement != null);
    }

    public boolean hasMoreElements() {
      return hasMore();
    }

    public InputStream next() {
      if (hasMore()) {
        InputStream res = nextElement;
        nextElement = null;
        return res;
      } else {
        throw new NoSuchElementException();
      }
    }

    public InputStream nextElement() {
      return next();
    }

    public void close() {
    }
  }
}
